Yumiko Yoshiki

Antioxidant compounds from bananas (Musa cavendish)

The antioxidant compounds from commercial bananas, Musa Cavendish, were studied. One of the antioxidants, gallocatechin, was identified in the banana. The gallocatechin was isolated (using HPLC) from the banana peel extract, which showed strong antioxidant activity. Gallocatechin was more abundant in peel (158 mg/100 g dry wt.) than in pulp (29.6 mg/100 g dry wt.). The antioxidant activity of the banana peel extract, against lipid autoxidation, was stronger than that of the banana pulp extract. This result was consistent with the gallocatechin analysis. The higher gallocatechin content may account for the better antioxidant effects. Thus, the antioxidant capacity of the bananas may be attributed to their gallocatechin content. Bananas should be considered as a good source of natural antioxidants for foods.

Saponins conjugated with 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one from phaseolus coccineus

From the hypocotyl of scarlet runner bean (Phaseolus coccineus), a new 2,3-dihydro-2,5,-dihydroxy-6-methyl-4H-pyran-4-one conjugated saponin, named soyasaponin alpha a, was isolated together with two known saponins, soyasaponin alpha g and beta g. Their structures were elucidated by 1H NMR and 13C NMR spectroscopy and chemical techniques.

MECHANISM OF CATECHIN CHEMILUMINESCENCE IN THE PRESENCE OF ACTIVE OXYGEN

The photon emission (chemiluminescence; CL) of catechin in the presence of active oxygen species (hydrogen peroxide, hydroxyl radical tert-butyl hydroperoxide and tert-butyl oxyl radical) and acetaldehyde was confirmed to occur non-enzymatically at room temperature in aqueous neutral conditions. The CL intensity [P] in the presence of active oxygen species (X), catalytic species (Y) and receptors (Z) is predicted by [P] = k [X] [Y] [Z]. The calculated photon constants (k) of 8 catechins and gallic acid were 8.23 x 10(6) M-2 s-1 counts ((-)-epigallocatechin), 2.78 x 10(8) ((-)-epigallocatechin gallate), 4.66 x 10(5) ((-)-gallocatechin gallate), 4.36 x 10(5) ((-)-gallocatechin), 2.70 x 10(5) ((-)-epicatechin), 6.44 x 10(4) ((-)-catechin), 585 x 10(4) ((-)-epicatechin gallate), 4.78 x 10(4) (gallic acid) and 3.54 x 10(4) ((-)-catechin gallate), respectively. The system of active oxygen species, catalytic species and receptors is proposed to be a scavenging mechanism for active oxygen species. In the presence of acetaldehyde, (-)-epigallocatechin (maximum k value among catechins tested) reacted with tert-BuOOH to form tert-BuOH as determined by HPLC analysis.

Effect of Heat Shock Preconditioning on ROS Scavenging Activity in Rat Skeletal Muscle after Downhill Running

The mechanisms of the protective effect conferred by heat shock preconditioning (HS) are currently unknown. The purpose of this study was to determine the effect of HS on muscle injury after downhill running and to address the mechanism of the effect. Female Wistar rats were assigned to three groups: HS, downhill running (E), and downhill running after heat shock preconditioning (HS + E). The HS and HS + E rats were placed in a heat chamber for 60 min (ambient temperature 42 +/- 1.0 degrees C) 48 h before downhill running. Reactive oxygen species (ROS) scavenging activity was determined by electron spin resonance (ESR), and heat shock protein 72 (HSP72) mRNA expression was measured in rat quadriceps femoris. Leukocyte infiltration and degenerated muscle fibers were determined histopathologically. ROS scavenging activity significantly increased at 3 days after HS (151 +/- 18%) and HSP72 mRNA expression increased immediately after HS (1750 +/- 1914%). No decrease in ROS scavenging activity was observed in the HS + E rats at 2 days after exercise compared with the E rats (102 +/- 9% vs. 79 +/- 5%). Degenerated muscle fibers in HS + E rats were significantly less than in E rats at 2, 3, and 7 days after exercise (0.8 +/- 1.0 vs. 2.8 +/- 1.6, 0.8 +/- 1.0 vs. 1.8 +/- 1.6, 0 vs. 0.3 +/- 0.6, respectively). These data demonstrated that HS can reduce muscle injury after downhill running, and this effect may be mediated by increased ROS scavenging activity. Furthermore, HS may protect the antioxidant defense system in skeletal muscle by enhancing the adaptive HSP72 mRNA response.

Chemiluminescence of Horseradish Peroxidase and Acetaldehyde Related with Gallic Acid and Hydrogen Peroxide Interaction

Abstract— This study focuses on the fact that the chemiluminescence in the visible region is emitted from the H2O2/gallic acid/ horseradish peroxidase (HRP) and the H2O2/gallic acid acetaldehyde (MeCHO) systems. The concentration dependence of chemiluminescence intensity that led to the different response of HRP and MeCHO toward H2O2 indicates that the photon emission participates with peroxidase activity including an electron transfer reaction. From our experimental results, in this study, we postulated a reaction process for chemiluminescence based on a one‐electron redox shuttle from H2O2 by peroxidase. The photon intensity and spectra data from the H2O2/ HRP and the H2O2/MeCHO systems with various cate‐chins were not only affected by HRP and MeCHO but also corresponded with the chemical structure of cate‐chins. The energy calculated from the spectra is 47–64 kcal/mol. These results suggested that the chemiluminescence of both systems arose from excited carbonyl compounds produced by an intermediate of the alkyl radical and the metal‐bound hydroxyl (compound II species). Hydroxyl radical inhibition, showing a notable increase from the gallic acid addition, makes the decay of the hydroxyl form of heme iron the most likely candidate for the chemiluminescence.

Chemiluminescence and reactive oxygen scavenging activities of the hydrogen peroxide/gallic acid/lactoperoxidase system.

Photon emission in the hydrogen peroxide/gallic acid/lactoperoxidase system was studied using visible region chemiluminescence. The photon emission intensity showed a pH-dependence curve with a maximum at pH 4.5-5.0. The spectral analysis showed to be at 510 nm and its energy was 61.0 kcal/mol at either pH 4.5 or pH 7.0. In addition, near-infrared spectral analysis at 1270 nm suggested that this photon emission from the hydrogen peroxide/gallic acid/lactoperoxidase system was produced without generation of (1)O(2). The gallic acid/lactoperoxidase system, based on the chemiluminescence system, has superoxide-, hydroxyl radical-scavenging activities and antioxidative activity. These results are strong evidence that the gallic acid/lactoperoxidase system is one of the reactive oxygen scavenging systems.

Generation of Reactive Oxygen Species and Photon Emission from a Browned Product

The properties of photon emission arising from a browned product were investigated. The photon intensity of the browned product was proportional to the absorbancy at 420 nm, and was influenced by the amino acid structure. The fluorescence spectrum showed similar compounds in the browned product to be related with this photon emission. Superoxide and hydrogen peroxide contributed highly to this photon emission, and several redox compounds enhanced the photon intensity at appropriate concentrations. Our work suggests that the photon intensity was closely related to the reactive oxygen species (ROS) generated from the browned product, and this effect may be utilized to evaluate the function and quality of browned food.

Triterpenoid saponins from Vigna angularis

Abstract Three new 2,3-dihydro-2,5-dihydroxy-6-methyl-4 H -pyran-4-one conjugated saponins, named AzII, AzIII and AzIV, were isolated from hypocotyls of adzuki beans ( Vigna angularis ). On the basis of chemical and spectral evidence, the structures of AzII, AzII and AzIV were established as 3- O -[ β - d -glucopyranosyl(1→2)- β - d -glucuronopyranosyl(1→2)- β - d -glucuronopyranosyl(1→)]-22- O -[2,3-dihydro-2,5-dihydroxy-6-methyl-4 H -pyran-4-one(2′→)]-3- β ,22 β ,24-trihydroxyolean-12-ene, 3- O -[ α - l -rhamnopyranosyl(1→2)- β - d -glucuronopyranosyl(1→2)- β - d -glucuronopyranosyl(1→)]-22- O -[2,3-dihydro-2,5-dihydroxy-6-methyl-4 H -pyran-4-one(2′→)]-3 β ,22 β ,24-trihydroxyolean-12-ene, and 3- O -[ β - d -glucopyranosyl(1→2)- β - d -glucopyranosyl(1→2)- β - d -glucuronopyranosyl(1→)]-22- O -[2,3-dihydro-2,5-dihydroxy-6-methyl-4 H -pyran-4-one(2′→)]-3 β ,22 β ,24-trihydroxyolean-12-ene, respectively.

Chemiluminescence properties of soybean protein fraction in the hydroperoxide and hydrogen donor system.

Whey fraction, a constituent of soybean protein, produced a photon emission in the presence of gallic acid and hydrogen peroxide. Identification of the chemiluminescence agent from the whey fraction indicated the participation of lipoxygenase in the emission. The reactivity of lipoxygenase with peroxides in the gallic acid solidus hydroperoxide system was in the order of methylethyl hydroperoxide (MEK-OOH, 4800 cps) > tert-butyl hydroperoxide (tert-BuOOH, 607 cps) > hydrogen peroxide (H(2)O(2), 455 cps) > cumene hydroperoxide (cumene-OOH, 261 cps). Emission maxima for H(2)O(2) and cumene-OOH were 670 nm, and emission maxima for MEK-OOH and tert-BuOOH were at 510 nm. The photon intensity from the gallic acid lipoxygenase system corresponded to the linoleic acid hydroperoxide value. A high correlation of photon intensity with hydroperoxide, including linoleic hydroperoxide was useful as a simple and sensitive method for the direct detection of hydroperoxides in biomaterials.

A saponin conjugated with 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one from Vigna angularis

Abstract A new 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one conjugated saponin, (Az I), was isolated from adzuki beans (Vigna angularis). 1H NMR and 13C NMR spectroscopy and chemical techniques showed the structure to be 3-O-[β- d -glucopyranosyl-(1 → 2)-β- d -glucuronopyranosyl-(1 → )]-22-O-[2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one-(2′ → )]-3β,22β,24-trihydroxyolean-12-ene.